Answer:
1. Fossils are essential to the geologic record because they provide evidence of past life and environmental conditions. They help scientists reconstruct the history of life on Earth, understand how species have evolved over time, and track changes in climate and geography. Fossils also provide insight into the origins of modern biodiversity and can be used to study the distribution and extinction of species.
2. Bipedalism emerged in hominins for a variety of reasons. One of the primary reasons is that it allowed hominins to free up their hands for tool use and other tasks. This was a significant advantage that likely contributed to the success of early hominins. Bipedalism also allowed hominins to cover long distances more efficiently and with less energy than quadrupedalism. Walking on two legs also allowed hominins to see farther over tall grasses and other obstacles. This would have been useful for spotting potential predators or prey. Additionally, bipedalism may have allowed hominins to regulate their body temperature more effectively by reducing direct exposure to the sun.
If humans walked on all fours instead of having hands, our lives would be significantly different. We would have much more limited abilities to manipulate objects, use tools, and communicate with others. Our vision and other senses would also likely be different, as our bodies would be structured differently to accommodate quadrupedal movement.